Bullous Lesions Crusts Erosions Macules Plaques & Scales Papules Pustules Nodules Vesicles Wheals Ulcers
•Herpes simplex
•Herpes zoster
•Dermatitis herpetiformis
•Bullous pemphigoid
•Pemphigus vulgaris
•Erythema multiforme
•Porphyria cutanea tarda
•Fixed drug eruptions
•Toxicodendron dermatitis (poison ivy, oak, sumac)
•Dermatophytic infection (tinea)
•Contact dermatitis
•Insect bite
•Dermatophytic infection (tinea)
•Toxic epidermal necrolysis
•Toxic-infectious erythemas
•Erythema multiforme
•Primary blistering disorders (bullous pemphigoid and pemphigus vulgaris)
•Brown recluse spider bite
•Drug eruption
•Tattoo (ink)
•Rheumatic fever
•Syphilis (secondary)
•Viral exanthema
•Toxic or infectious erythemas
•Meningococcemia (early)
•External trauma (ecchymosis)
•Tinea versicolor
•Cellulitis (early)
•Chronic cutaneous
(discoid) lupus
•Tinea corporis
•Paget’s disease
•Lichen planus
•Cutaneous T-cell lymphoma
•Pityriasis rosea
•Secondary syphilis
•Bowen’s disease
•Basal cell carcinoma
•Molluscum contagiosum
•Skin tags
•Atopic dermatitis
•Insect bite
•Toxicodendron dermatitis (poison ivy, oak, sumac)
•Erythema multiforme
•Varicella (early)
•Hidradenitis suppurativa
•Herpetic infection (herpes simple herpes zoster, varicella)
•Pyoderma gangrenosum
•Basal cell carcinoma
•Squamous cell carcinoma
•Metastatic carcinoma
•Erythema nodosum
•Herpetic infection (herpes simplex, herpes zoster, varicella)
•Toxicodendron dermatitis (poison ivy, oak, sumac)
•Thermal burn
•Friction blister
•Ttoxic epidermal necrolysis
•Bullous pemphigoid
•Pemphigus vulgaris
•Insect bite
•Erythema multiforme
•Aphthous lesions
•Decubitus ulcer
•Thermal or friction injury
•Subacute or chronic ischemia
•Chancre (primary syphilis)
•Primary blistering disorders (bullous pemphigoid and pemphigus vulgaris)
•Brown recluse spider bite
•Pyoderma gangrenosum
•Stasis ulcer
•Factitial ulcer

Lesion Terms & DDx

Lesion Morphology
Descriptor Morphology Definition Lesion Nature Height Relative to Adjacent Skin Differential Considerations Image
Abscess Tender, erythematous, fluctuant nodule   Primary Elevated  
Bulla Circumscribed, thin-walled, elevated blister >5 mm in diameter   Primary Elevated Bullous impetigo
Toxicodendron dermatitis (poison ivy, oak, sumac)
Thermal burn
Friction blister
Toxic epidermal necrolysis
Bullous pemphigoid
Pemphigus vulgaris

Comedo Papule with an impacted pilosebaceous unit   Primary Elevated  
Crust         Eczema
Dermatophytic infection (tinea)
Contact dermatitis
Insect bite
Cyst Sack containing liquid or semisolid material   Primary Elevated  
Excoriation Linear marks from scratching   Secondary Flat  
Erosion Ruptured vesicle or bulla with denuded epidermis   Secondary Depressed Candidiasis
Dermatophytic infection (tinea)
Toxic epidermal necrolysis
Toxic-infectious erythemas
Erythema multiforme
Primary blistering disorders (bullous pemphigoid and pemphigus vulgaris)
Brown recluse spider envenomation

Fissure Linear cracks on skin surface   Secondary Flat  
Macule Flat, circumscribed discoloration 1 cm in diameter; color varies Adjective referring to macules which are circumscribed changes in the color of skin that are neither raised (elevated) nor depressed. Macules are never large. They are little spots or blemishes in the skin. They are entirely flat and can only be appreciated by visual inspection; they cannot be seen from the side Primary Flat Drug eruption (fixed or photosensitive)
Nevus, tattoo (ink)
Rheumatic fever
Syphilis (secondary)
Viral exanthema
Toxic or infectious erythemas,
Meningococcemia (early)
External trauma (ecchymosis)
Tinea versicolor
Cellulitis (early)
Nodule Palpable solid lesion <1 cm in diameter   Primary Elevated Basal cell carcinoma
Squamous cell carcinoma
Metastatic carcinoma
Erythema nodosum
Papule Elevated, solid, palpable lesion <1 cm in diameter; color varies a small, raised, solid pimple or swelling, often forming part of a rash on the skin and typically inflamed but not producing pus Primary Elevated Acne
Basal cell carcinoma
Molluscum contagiosum
Skin tags
Atopic dermatitis
Insect bites
Toxicodendron dermatitis (poison ivy, oak, sumac)
Erythema multiforme
Varicella (early)

Petechiae Nonblanching purple spots <2 mm in diameter   Primary Flat  
Plaque Flat-topped elevation formed by confluence of papules >0.5 cm in diameter   Primary Elevated Eczema
Pityriasis rosea
Tinea corporis and versicolor
Seborrheic dermatitis
Syphilis (secondary)
Erythema multiforme

Purpura Nonblanching purple discoloration of the skin   Primary Flat  
Pustule Vesicle containing purulent fluid   Primary Elevated Acne
Hidradenitis suppurativa
Herpetic infection (herpes simplex, herpes zoster, varicella)
Pyoderma gangrenosum

Scales         Psoriasis
Pityriasis rosea
Toxic and infectious erythemas
Syphilis (secondary)
Dermatophytic infection (tinea)
Tinea versicolor
Xerosis (dry skin)
Thermal burn (first degree)
Scar Sclerotic area of skin   Secondary Flat or elevated  
Sclerosis Firm, indurated skin   Secondary Flat or elevated  
Telangiectasia Small, blanchable superficial capillaries   Primary Flat  
Tumor Palpable solid lesion >1 cm in diameter   Primary Elevated  
Ulcer Epidermal or dermal tissue loss   Secondary Depressed Aphthous lesions
Decubitus ulcer
Thermal or friction injury
Subacute or chronic ischemia
Chancre (primary syphilis)
Primary blistering disorders (bullous pemphigoid and pemphigus vulgaris)
Brown recluse spider envenomation
Pyoderma gangrenosum
Stasis ulcer
Factitial ulcer
Vesicle Circumscribed, thin-walled, elevated blister <5 mm in diameter   Primary Elevated Herpetic infection (herpes simplex, herpes zoster, varicella)
Toxicodendron dermatitis (poison ivy, oak, sumac)
Thermal burn
Friction blister
Ttoxic epidermal necrolysis
Bullous pemphigoid
Pemphigus vulgaris

Wheal Transient, edematous papule or plaque with peripheral erythema   Primary Flat or elevated Urticaria
Insect bites
Erythema multiforme


Common Conditions & Tx

Dx Image Comments/Management
Erythema Migrans Caused by Borrelia burgdorferi, which is transmitted by the tick Ixodes  (also vectorfor Babesia). Natural reservoir is the mouse. Mice are important to tick life cycle. Common in northeastern United States. ƒƒ
Initial symptoms—erythema chronicum migrans, flu-like symptoms, +/- facial nerve palsy.
Later symptoms—monoarthritis (large joints) and migratory polyarthritis, cardiac (AV nodal block), neurologic (encephalopathy, facial nerve palsy, polyneuropathy).
Treatment: doxycycline, ceftriaxone

FAKE a Key Lyme pie:
Facial nerve palsy (typically bilateral)
Kardiac block
Erythema migrans

Erythema Nodosum
Painful inflammatory lesions of subcutaneous fat, usually on anterior shins. Often idiopathic, but can be associated with:
  • Sarcoidosis
  • Coccidioidomycosis
  • Histoplasmosis
  • TB
  • Streptococcal infections
  • Leprosy and
  • Crohn disease
Erythema Multiforme
Associated with
  • Infections (e.g., Mycoplasma pneumoniae, HSV),
  • Drugs (e.g., sulfa drugs, β-lactams, phenytoin),
  • Cancers, and
  • Autoimmune disease.

Presents with multiple types of lesions—macules, papules, vesicles, and target lesions (look like targets with multiple rings and a dusky center showing epithelial disruption)


  • Systemic steroids are commonly used for localized disease and provide symptomatic relief.
  • A short, intensive steroid course of prednisone, 60 to 80 mg PO once a day, particularly in drug-related cases, with abrupt cessation in 3 to 5 days if no favorable response is noted.
  • Systemic analgesic agents and antihistamines provide symptomatic relief.
  • Stomatitis:
    • Diphenhydramine and viscous lidocaine mouth rinses.
    • Caution is advised with oral lidocaine due to its neurotoxicity if excessively applied.
  • Blisters:
    • Cool compresses moistened with Burow solution (5% aluminum acetate).
    •  Ocular involvement should be monitored by an ophthalmologist.
    • Unfortunately, burst steroid therapy does not appear to reduce the chance of development or significance of existing ocular lesions
Granuloma annulare

- Granuloma annulare manifests as a ring of firm, flesh-colored or red papules with a more prominent outer ring forming due to central involution.
- These lesions may last for months to years.
- The distribution is usually on the dorsolateral aspect of the hands or feet.

Key Factors:
- asymptomatic grouped annular pink or flesh-colored dermal papules
- flesh-colored, pink, or brown macules or small papules
- soft-tissue nodules
- perforating papules, crusting or ulcerated lesions
- erythematous patches

Diagnostic Tests
1st Tests To Order
- clinical diagnosis
- skin biopsy
- fasting blood sugar
- thyroid function tests
- lipid screening
- hepatitis screen
- HIV testing

- Clobetasol topical : (0.05%) apply a small amount to the affected area(s) once daily (or once weekly if occlusive dressing is used) for up to 8 weeks, maximum 50 g/week # 45g
- Triamcinolone acetonide : (5 mg/mL) 0.1 mL intralesionally every 6-8 weeks; two to three treatments are usually sufficien

Pyoderma gangrenosum
- Pyoderma gangrenosum begins as a tender papule, usually on the lower leg, and evolves to a painful, necrotic, inflammatory lesion that gradually enlarges up to 10 cm.
- It usually is a manifestation of an underlying systemic inflammatory condition such as inflammatory bowel disease.
- The lesions last for months to years and heal with scarring.

- Patients with pyoderma gangrenosum usually describe the initial lesion as a bite reaction, with a small, red papule or pustule changing into a larger, ulcerative lesion.
--> Often, patients give a history of a brown recluse or other spider bite, but they have no evidence that a spider actually caused the initial event.
- Pain is the predominant complaint.
- Arthralgias and malaise.
- Commonly associated diseases include:
  - Inflammatory bowel disease.
  - Leukemia or preleukemic states, predominantly myelocytic in nature or monoclonal gammopathies.
  - Psoriatic arthritis, Osteoarthritis, and spondyloarthropathy
  - Hepatitis & primary biliary cirrhosis
  - Myelomas (IgA type predominantly)
  - Lupus erythematosus & Sjögren syndrome

- CBC, CMP, LFT (PT/INR), UA, Hepatitis panel, VDRL, antineutrophil cytoplasmic antibody test, a partial thromboplastin time test, and an antiphospholipid antibody test to rule out Wegener granulomatosis, vasculitis, and antiphospholipid antibody syndrome.
- Tissue culture, CXR, Dopper (Venous)
- Colonoscopy (R/O IBS)

-Topical therapies include:
 - Gentle local wound care and dressings,
 - Superpotent topical corticosteroids
 - Cromolyn sodium 2% solution,
 - Nitrogen mustard, and
 - 5-aminosalicylic acid.
- The topical immune modifiers tacrolimus and pimecrolimus may have some benefit in certain patients.

-Systemic therapies include:
 - corticosteroids,
 - cyclosporine
 - Mycophenolate mofetil
 - Azathioprine
 - Dapsone,
 - Tacrolimus,
 - Cyclophosphamide
 - Chlorambucil
 - Thalidomide|
 - Tumor necrosis factor-alpha (TNF-alpha) inhibitors, and nicotine.

-Intravenous (IV) therapies include:
 - Pulsed methylprednisolone
 - Pulsed cyclophosphamide
 - Infliximab
 - IV immunoglobulin
 - Ustekinumab.

- Other therapies include hyperbaric oxygen

- Surgery should be avoided, if possible, because of the pathergic phenomenon that may occur with surgical manipulation or grafting, resulting in wound enlargement.
- In some patients, grafting has resulted in the development of pyoderma gangrenosum at the harvest site.
- In cases in which surgery is required, the best plan, if possible, is to have the patient on therapy in order to prevent pathergy.
- Some patients with ulcerative colitis have responded to total colectomy; in other patients, however, the disease is peristomal and occurs following bowel resection


Key Factors:
- erythematous edematous lesions
- pruritus
- resolution within 24 hours
- swelling of face, tongue, or lips
- blanching lesions
- stridor

Diagnostic Tests
- CBC with differential, CMP,  urinalysis, ESR, CRP, anti-IgE receptor antibody and related tests, TSH, antithyroid antibodies, antinuclear antibodies (ANA), serum protein electrophoresis (SPEP), Helicobacter pylori antibody, skin prick testing for specific food allergens, in vitro IgE testing for specific food allergens, skin biopsy,
- C4 level
- C1-esterase inhibitor level
- C1-esterase inhibitor function
- C1q levels

- Trigger avoidance
- [If airway involved] Epinephrine : 0.3 mg (1:1000) intramuscularly every 1-2 hours when required

- H1 Blocker:
Primary Options:
loratadine : 10 mg orally once daily OR
desloratadine : 5 mg orally once daily OR
cetirizine : 10 mg orally once daily OR
levocetirizine : 5 mg orally once daily OR
fexofenadine : 180 mg orally once daily
Secondary Options
diphenhydramine : 25-50 mg orally every 4-6 hours when required OR
hydroxyzine : 10-100 mg orally every 6 hours when required OR
chlorpheniramine : 4 mg orally every 4-6 hours when required OR
doxepin : 10-100 mg orally once daily at bedtime when required

- H2 Blocker:
Primary Options
ranitidine : 150 mg orally twice daily
Secondary Options
Cimetidine : 200-800 mg orally twice daily


- methylprednisolone sodium succinate : children: 0.5 to 1.7 mg/kg/day intravenously given in divided doses every 6-12 hours; adults: 10-40 mg by intravenous infusion initially, followed by 40-120 mg once daily thereafter
- prednisone : 0.5 to 1 mg/kg/day orally given in 1-2 divided doses for 5-7 days

Leukotriene-receptor blocker:
Zafirlukast : 20 mg orally twice daily
montelukast : 10 mg orally daily

- The lesions usually heal without scarring over a 10- to 14-day period

Steven-Johnson Syndrome